warm up 1. 14,000 is 2 % of what number? 2. 39 is 13% of what number?

Percent Increase and Decrease6-4 Students will be able to determine percent decrease.

Warm Up

1. 14,000 is 2 % of what number?2. 39 is 13% of what number?3. 37 % of what number is 12?4. 150% of what number is 189?

560,00030032

12

126

12


Problem of the DayIn a school survey, 45% of the students said orange juice was their favorite juice, 25% preferred apple, and 10% preferred grapefruit. The remaining 32 students preferred grape juice. How many students participated in the survey?160 students


Learn to find percent increase and decrease.


Percent decrease describes how much the original amount decreases.

amount of changeoriginal amount=percent decrease

100


Find the percent increase or decrease from 16 to 12.

Additional Example 1: Finding Percent Increase or Decrease

This is percent decrease.16 – 12 = 4 First find the amount of change.

Think: What percent is 4 of 16?

amount of decrease original amount

416 Set up the ratio.


Additional Example 1 Continued

= 25% Write as a percent.

= 0.25 Find the decimal form.416

From 16 to 12 is a 25% decrease.


Find the percent increase or decrease from 15 to 20.

Check It Out: Example 1

This is percent increase.

20 – 15 = 5 First find the amount of change.


amount of increase original amount

520 Set up the ratio.


Check It Out: Example 1 Continued


= 0.25 Find the decimal form.520

From 15 to 20 is a 25% increase.


When Jim was exercising, his heart rate went from 70 beats per minute to 98 beats per minute. What was the percent increase?

Additional Example 2A: Life Science Application


28 70 Set up the ratio.




Additional Example 2 Continued


= 0.4 Find the decimal form. 70 28

Jim’s heart rate increased by 40% when he exercised.


In 1999, a certain stock was worth $1.25 a share. In 2002, the same stock was worth $0.85 a share. What was the percent decrease?

Additional Example 2B: Application

1.25 – 0.85 = 0.40 First find the amount of change.

Think: What percent is 0.40 of 1.25?

amount of decreaseoriginal amount 1.25

0.40Set up the ratio.


Additional Example 2B Continued


= 0.32 Find the decimal form. 1.25 0.40

The value of the stock decreased by 32%.


When Jeff was watching TV, the number of times his eyelids blinked went from 50 blinks per minute to 75 blinks per minute. What was the percent increase?

Check It Out: Example 2A


25 50 Set up the ratio.





= 0.5 Find the decimal form. 50 25

The blinking of Jeff’s eyelids increased by 50% when he watched TV.

Check It Out: Example 2A Continued


In 2000, a certain stock was worth $9.00 a share. In 2003, the same stock was worth $3.80 a share. What was the percent decrease, to the nearest tenth?

Check It Out: Example 2B

9.00 – 3.80 = 5.20 First find the amount of change.

Think: What percent is 5.20 of 9.00?

amount of decreaseoriginal amount 9.00

5.20Set up the ratio.


The value of the stock decreased by about 57.8%.

9.005.20 = 0.57 Find the decimal form.

= 57.7% Write as a percent.

Check It Out: Example 2B Continued


Sarah bought a DVD player originally priced at $450 that was on sale for 20% off. What was the sale price?

Additional Example 3A: Using Percent Change to Find Discounts and Markups

$450 20% First find 20% of $450.$450 0.20 = $9020% = 0.20The amount of decrease is $90.Think: The reduced price is $90 less than $450.$450 – $90 = $360 Subtract the amount of decrease.The sale price of the DVD player was $360.


Mr. Olsen has a computer business in which he marks everything up 40% above the wholesale price. If he purchased a printer for $85 wholesale, what will be the retail price?

Additional Example 3B: Using Percent Change to Find Discounts and Markups

$85 40% First find 40% of $85.$85 0.40 = $34 40% = 0.40The amount of increase is $34.Think: The retail price is $34 more than $85.$85 + $34 = $119 Add the amount of increase.

The retail price of this printer will be $119.


Lily bought a dog house originally priced at $750 that was on sale for 10% off. What was the sale price?

Check It Out: Example 3A

$750 10% First find 10% of $750.$750 0.10 = $7510% = 0.10The amount of decrease is $75.Think: The reduced price is $75 less than $750.$750 – $75 = $675 Subtract the amount of

decrease.The sale price of the dog house was $675.


Barb has a grocery store in which she sells everything at 50% above the wholesale price. If she purchased a prime rib for $30 wholesale, what will be the retail price?$30 50% First find 50% of $30.$30 0.50 = $15 50% = 0.50The amount of increase is $15.Think: The retail price is $15 more than $30.$30 + $15 = $45 Add the amount of increase.

The retail price of the prime rib will be $45.

Check It Out: Example 3B


Standard Lesson Quiz

Lesson Quizzes

Lesson Quiz for Student Response Systems


Lesson QuizFind each percent increase or decrease to the nearest percent.

1. from 12 to 15 2. from 1625 to 14003. from 37 to 1254. from 1.25 to 0.855. A computer game originally sold for $40 but is now on sale for 30% off. What is the sale price of the computer game?

14% decrease25% increase

238% increase32% decrease

$28


1. Identify the percent increase or decrease to the nearest percent.from 23 to 29

A. 26% decrease

B. 26% increase

C. 32% decrease

D. 32% increase



2. Identify the percent increase or decrease to the nearest percent.from 1440 to 1220

A. 15% decrease

B. 15% increase

C. 28% decrease

D. 28% increase



3. A winter coat originally sold for $75 but is now on sale for 20% off. What is the sale price of the winter coat? A. $55

B. $60

C. $65

D. $70


warm up 1. 14,000 is 2 % of what number? 2. 39 is 13% of what number?

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